Reefing down a click or two tighter on the magazine cap can lower the point of impact a surprising amount on a high shooting gun. I've also bent barrels and reamed chokes eccentricly to bring poi to poa. I simply would not tolerate anything worse than a 60/40 pattern.
I've never heard that. I usually tighten my magazine cap to the point of getting that last detent click.
As far as a shotgun that doesn't shoot at least 60/40, I stopped using my Benelli Super Nova for that very reason. Not sure what it prints, but its way worse than 60/40. Maybe 70/30 or worse. I've got some new Carlsons chokes for it I haven't tried. Maybe those will help.
